Application of the DDM and fracture mechanics model on the simulation of rock breakage by mechanical tools

A DDM (displacement discontinuity method) program coupled with a modified energy criterion is used to simulate the development of cracks and chips by indentation tools. In our analysis a cavity model is applied to represent the expansion of crushed rock to the surrounding rock and the cracks are formedin two-dimensional and quasi-static conditions. The model parameters, rock properties and load magnitudes are varied in the numerical calculations. The results show that chips are formed by multiple mechanisms of either tension or shear, or their combinations. The cracks may either propagate to the free surface to form chips or rest in the rock subsurface. The crack development is dependent upon rock and fracture properties, loading force and tool characteristics. The DDM is a convenient tool in the study of rock fragmentation and cracks.     

A review of rock mechanics studies in the United States pertinent to earthquake prediction

Premonitory phenomena such as dilatancy, creep, acoustic emission, and changes in seismic velocity and attenuation, electrical resistivity, magnetic moment, and gas emission, which occur before fracture of initially intact rock and before stick-slip on faults or between finely ground surfaces of rock, have been reviewed and discussed in relation to earthquake prediction. This review is restricted to the results of laboratory experiments that have been carried out in the United States of America.     

The effect of water on stress relaxation of faulted and unfaulted sandstone

A series of stress relaxation experiments have been carried out on faulted and intact Tennessee sandstone to explore the influence of pore water on strength at different strain rates. Temperatures employed were 20, 300 and 400°C, effective confining pressure was 1.5 kb and strain rates as low as 10^–10 sec^–1 were achieved. Most samples were prefaulted at 2.5 kb confining pressure and room temperature. This is thought to have secured a reproducible initial microstructure.The strength of the dry rock was almost totally insensitive to strain rate in the range 10^–4 to 10^–10 sec^–1. In contrast, the strength of the wet rock decreased rapidly with strain rate at rates less than 10^–6 sec^–1. Brittle fracture of the quartz grains which constitute this rock is the most characteristic mode of failure under the test conditions used.The experimental data are discussed in terms of the possible deformation rate controlling processes, and it is suggested that in the wet experiments at intermediate to high strain rates (10^–7 to 10^–4 sec^–1) the observed deformation rate is controlled by the kinetics of water assisted stress corrosion, whilst deformation at low strain rates (ca. 10^–9 sec^–1) is controlled by a pressure solution process.The results have implications for the rheology of fault rocks at depths of perhaps 10 to 15 km in sialic crust.     

Velocities of elastic waves andv P/v S ratios in dry and water-saturated rock samples at high pressure

Elastic wave velocities and the ratiov _P/v _S were studied for dry and initially saturated samples of carbonate and crystalline rocks at pressures to 2 kbar. In initially saturated samplesv _P increases in crystalline rock, whereas in sedimentary rock it may either increase or decrease with increasing pressure. Under the same conditionsv _S remains approximately constant in crystalline rocks and decreases in sedimentary samples. The ratiov _P/v _S as a function of pressure increases in dry rocks and decreases in saturated ones. Saturated samples always have higherv _P/v _S ratios than dry ones. It appears that the geometry of the pore space influences the acoustic properties of saturated crystalline rocks.     

珠江三角洲年际潮差长期变化趋势

对20世纪50年代以来珠江三角洲网河内17个主要控制水文站的年际潮差变化趋势进行了显著性检验和突变点分析.通过Trend Free Pre-Whitening方法削除了水文时间序列中的自相关成分,利用非参数的Mann-Kendall检验研究了珠江三角洲年均潮差的变化趋势,指出潮差在珠江三角洲的变化趋势存在着空间变异性.在网河内的中、上游河段,潮差呈现明显的增大趋势,且越往上游,潮差的增大趋势越为显著;而在下游的口门区,由于受到围垦等人类活动影响,大部分站点的潮差表现为显著的下降趋势.Pettitt检验的结果表明,珠江三角洲潮差发生突变的时间段主要在20世纪80年代,这基本与河网内大规模的无序采沙开始的时间是同步的,表明挖沙是引起珠江三角洲内潮差变异的主导因素.潮差显著增大的趋势表明航道网内潮流动力明显增强,这亦是近年来珠江三角洲咸潮频发的机理原因之一.     

极震区岩体地震动力破坏研究体系框架浅析

极震区岩体地震动力破坏是造成极震区严重的地震地质灾害和次生灾害的根本原因。汶川地震中因此而导致的交通工程结构损坏、中断和次生崩滑流、堰塞湖等地质灾害,不仅加剧了灾害损失,并给震后的灾区恢复重建和对外交通遗留了较多的安全隐患。从岩体稳定、山体稳定和区域稳定的层次,分别对有关极震区岩体地震动力破坏的主要研究成果进行了系统总结,分析了其现状和存在的问题。结合对研究思路和方法论的讨论,构建了极震区岩体地震动力破坏研究的体系框架,提出了极震区岩体地震动力破坏研究的主要内容和方向,以期明晰概念,理清思路,为有关问题的深入研究提供有益的参考。     

云南孟连芒信金矿成因探讨

芒信金矿脉状、透镜状、串球状金矿体,赋存于石炭系碳酸盐岩破碎带中。以裂隙金、晶隙金、固溶金、吸附金状存在。经历沉积—变质—岩浆活动等阶段。     

保山西邑铅锌矿采选工程RQD与RBI对比研究

用岩石质量指标和岩体块度指数的理论,对钻孔岩心实测资料进行分析和对比研究,对钻孔周围岩体进行分级。结果表明:岩体块度指数在岩石质量评价中能更准确地反映其优越性,具有更为显著的工程意义。     

华南成矿省（云南部分）堆积型铝土矿典型矿床

云南堆积型铝土矿典型矿床称为卖酒坪式,成矿物质来源于吴家坪组或龙潭组原生沉积铝土矿／岩层。矿床分布于与矿源层邻近的下伏中、上泥盆统一下二叠统中发育的溶丘漏斗、溶蚀坡地、石牙坡地和峰丛谷地等4种岩溶地貌类型中。岩溶地貌对堆积体厚度及形态起控制作用,各堆积类型Al2O3、A／S和含矿率均有一定规律。     

黄河黑山峡大柳树坝坝址岩体渗漏量及灌浆量数值模拟研究

大坝坝址岩体的渗漏研究对于大坝的安全运营至关重要。在进行渗漏治理的措施中,灌浆是常见的一种,但目前确定灌浆的各项参数,如配合比,孔距等,需通过灌浆试验花费大量的人财物力及时间才能确定。为快速查清每一种灌浆方案所灌浆量,本文针对模拟坝址水库渗漏灌浆效果的三维数值模拟开展了计算研究。在对大柳树坝坝址岩体地质情况及渗漏情况分析的基础上,将蓄水前的地下水运移规律模拟出,与实际通过钻孔平硐资料及分析得出的实际地下水运移规律做比较,验证对地下水运移规律的假设;然后将蓄水后的地下水运移规律模拟出,确定地下水的运移规律,了解地下水运移的方向,验证与根据实际情况初步判断的地下水运移方向是否吻合;最后通过数值模拟确定在一定灌浆浆液配合比的情况下所需灌浆量与实际的灌浆试验结果做比较。得出结果与实际灌浆试验结果吻合,证明通过数值模拟,建立浆液配合比与灌浆效果之间的关系,在类似情况快速地选取配合比是可行的。